Valved bags



Oct. 5, 1965 F. WALKER 3,209,804

VALVED BAGS Filed April 19, 1962 F|G.| 5 FIG. 2 30 FIG.3 39 FIG.4 39

INVENTOR FRANK WALKER M @MLZV M ATTORNEYZ United States Patent 3,209,804 VALVED BAGS Frank Walker, Stevenage, England, assignor to Iintrsh Visqueen Limited, London, England, a corporation of Great Britain Filed Apr. 19, 1962, Ser. No. 188,767 Claims priority, application Great Britain, Apr. 28, 1961, 15,459/61; Dec. 6, 1961, 43,703/61 7 Claims. (Cl. 150-9) This invention relates to valved bags suitable for containing granular solid and to processes for their manufacture.

In this specification the term bag is intended not to be limited to bags of any particular shape or size, but to cover bags, sacks and flexible containers in general which have the special features of this invention.

This invention consists in a valved bag of thermoplastic material, having an aperture in the wall of the bag near to one end of the said wall, and a patch-piece secured to the bag wall which covers the aperture and defines a filling sleeve between the bagwall and the patch-piece through which the bag can be filled, the dimensions and arrangement of the aperture and filling sleeve with respect to the bag wall being such that, when the closed bag filled with a granular solid is inverted so that the contents press on the sleeve, substantially none of the contents escape through the sleeve.

The patch-piece is preferably of the same material and of the same thickness as the bag walls.

It is to be understood that the finished valved bag will normally be closed at both ends, leaving the valve, formed by the aperture and filling sleeve, as the only place of entry into the bag.

In practice, the choice of suitable dimensions and arrangement of the aperture and filling sleeve with respect to the bag can be made after simple experiment. Thus, the material or materials intended to be packed may be filled into a bag provided with the proposed valve, and the filled bag subjected to handling and treatment simulating that likely to be encountered in normal usage. If significant leakage of the material through the valve occurs during such handling and treatment, the valve should be suitably modified, for example by increasing the length of the sleeve; on the other hand, the experiments may suggest, and further experiments confirm, that an economy can safely be effected by reducing the size of the sleeve.

In general, the narrower and longer the sleeve the less is the risk of the contents of the bag escaping when the latter is inverted after being filled. However, the sleeve must of course be wide enough to accommodate the filling spout to be used in filling the bag and this consideration normally limits the narrowness of sleeve which is acceptable in practice. The length of the sleeve should preferably be such that it allows a filling spout to be inserted through the length of the sleeve and the aperture and to protrude into the interior of the bag.

The patch-piece may be secured to the outer or to the inner surface of the bag wall. In the former case, the filling sleeve is defined between the patchpiece and the outer surface of the Wall, and the aperture in the wall forms the internal opening of the valve; in the latter case, the filling sleeve is defined between the patch-piece and the inner surface of the wall, and the aperture in the wall forms the external opening of the valve. The valve apertures are preferably transverse to, though not necessarily at right-angles to, the adjacent edge of the bag.

It is generally preferable for the sleeve to be so positioned with respect to the bag wall that a filling spout can be inserted through the sleeve into the top of the bag whereby the bag can be filled as completely as possible ice before the level of its contents reaches the level of the sleeve; this can conveniently be achieved by so securing the patch-piece to the bag wall that the sleeve lies across the width of the bag and as near to the top edge of the bag wall as is practicable. However, the top edge of the patch-piece is preferably at a suficient distance below the top edge of the bag wall for the necessity of sealing together varying thicknesses of thermoplastic material when the bag is closed to be avoided; in other words, the patchpiece is preferably seamed to the bag wall by seams that are each distinct from the seams between the opposed walls of the finished bag. This is particularly advantageous when the bags is of polythene or a similar thermoplastic material to be subsequently closed by heat sealing, since heat-seal seams through a varying number of thicknesses are liable to have points of weakness where the number of thicknesses changes.

The security of the valve may be increased by the provision of an extension piece of thinner material than the patch-piece or bag walls (the patch-piece and bag walls preferably being formed from the same material and of the same thickness) secured to the free edge of the inner end of the filling sleeve. Thus, when the patch-piece is secured to the outer surface of the bag wall, the extension piece will be secured to the edge of the aperture in the bag wall opposite to the edge to which the patch-piece is secured, to cover the aperture internally. When the patch-piece is secured to the inner surface of the wall, the extension piece will be secured to the end of the patchpiece, further from the aperture through the bag wall. The extension piece is preferably formed from the same thermoplastic material as the bag walls, and for polythene is preferably from 0.0015 to 0.002 inch in thickness, although flaps in thicknesses up to 0.005 inch have been found to function efiiciently. Polythene film used for sack manufacture generally has a thickness of from 0.006 to 0.012 inch and flaps of a thickness just described are particularly suitable for use with such sacks.

Added security may alternatively be obtained by forming short, preferably parallel cuts into the free edge of the inner end of the filling sleeve (that is, into the free edge of the patch-piece or the bag wall, as the case may be) to form a number of fingers at the end of the sleeve.

Various embodiments of the invention are shown in the accompanying drawings, of which:

FIGURE 1 illustrates a bag with a valve formed by an aperture and an externally applied patch-piece, with extension flap;

FIGURE 2 illustrates a bag with a valve formed by an aperture and an internally applied patch-piece, with extension flap; and

FIGURES 3 and 4 illustrates bags each with a valve formed by an aperture and an externally applied patchpiece, the bag of FIGURE 4 having the edge of the aperture cut to form a number of fingers.

In FIGURE 1, 1 represents the side fold of the sack, which is formed from a length of tubular film of polythene; 2 represents one side of an aperture cut in the wall of the sack, shortly beyond which the edge of an external patch-piece 3 is secured along one of its edges at 4 to the wall of the sack; 5 and 6 are seams joining the side edges of the patch-piece to the wall of the sack; 7 is the external opening of the filling sleeve formed between the bag wall and the patch-piece; 8 is the second edge of the aperture through the wall of the sack, close to which, at 9, is secured one edge of the flap, 10, formed of the same material as the sack but in a thinner gauge; and 11 is the top seam of the sack, which joins the opposed walls and which is formed after the patch-piece and flap have been seamed into position.

In FIGURE 2, 21 represents the side fold of the sack,

which is formed from a length of tubular film of polythene; 22 represents one side of an aperture cut in the wall of the sack, shortly beyond which the edge of an internal patch-piece, 23, is secured along one of its edges, at 24, to the inner surface of the wall of the sack; 25 and 2.6 are seams joining the side edges of the patch-piece to the wall of the sack; 27 is the aperture in the Wall of the sack, which is the opening into the sleeve formed between the bag wall and the patch-piece; 28 is an extension piece, of thinner material than the patch-piece, seamed to the edge of the patch-piece at 29; and 30 is the top seam of the sack, which joins the opposed walls and which is formed after the patch-piece, with its extension, has been seamed into position.

In FIGURES 3 and 4, 31 represents the side fold of the sack, which again is formed from a length of tubular film of polythene; 32 is one side of an aperture in the Wall of the sack, shortly beyond which the edge of an external patch-piece 33 is secured along one of its edges at 34 to the wall of the sack; 35 and 36 are seams joining the side edges of the patch-piece to the wall of the sack. 37 in FIGURE 3 and 37' in FIGURE 4 represent the external opening of the filling sleeve formed between the bag wall and the patch-piece; 38 in FIGURE 4, are fingers formed between transverse cuts extending into the bag wall from the aperture; and 39 in each figure is the top seam of the sack.

Many modifications may be made in the bags particularly described in illustrating this invention. For example, although the aperture through the wall of each of the bags illustrated is a straight slit, it may be a wider aperture or a slit of another shape. In particular, where the aperture forms the external opening of the valve, the edge of the aperture not attached to the patch-piece may be of concave arcuate shape, as shown for the patch-piece in FIGURE 3; this enables a filling nozzle to be inserted more easily and generally ensures that the valve flattens itself more tightly against the wall of the filled bag, reducing the risk of tearing. This effect may be obtained, for example, by forming the aperture as a slit of arcuate shape, or by forming a wider aperture having one straight edge and one concave arcuate edge. The valve extension piece of bags of the type shown in FIGURES 1 and 2 is preferably secured to the end edge of the patch-piece along the whole length of the latter, as shown, but it may also be secured to the bag wall at one or more points to prevent it from folding back upon the patch-piece and becoming ineffective; this further seaming, however, is generally found to be unnecessary.

For ease of filling by conventional machines, it is normally preferred that the external aperture of the valve be substantially at right angles to the top of the bag. The internal aperture, may also be at right angles to the top of the bag; but it is often advantageous to design the valve so that the internal aperture is at another angle to the top of the bag, to assist filling or to ensure eificient sealing by the contents when the bag is removed from the filling machine by a particular technique. The best angles, and hence the preferred angle of the aperture and the preferred shape of the patch-piece, may be determined for particular applications by experiment under Working conditions.

The thermoplastic material used for the bags of the invention is conveniently a flexible sheet or film of a suitable thermoplastic polymer, bearing a heat-seal coating if desired. However, the term thermoplastic material as used in this specification includes flexible material comprising a layer of a thermoplastic polymer carried on a suitable flexible support, for example cloth or paper, the flexible material being such that two layers of it can be bonded together by a process of heat-sealing. An example of such a material is that consisting of cartridge paper coated on one or both sides with a suitable thermoplastic polymer.

Thermoplastic polymers suitable for the valved bags of the invention include polyolefins, for instance polythene (polyethylene) and polypropylene; polyvinyl chloride; polyethylene terephthalate and similar linear polyesters; and nylon. Polythene and polyvinyl chloride film are particularly suitable for the production of sacks. The thickness of the thermoplastic material used for the bags depends to a large extent upon the purpose to which the bags are to be put and the precise process by which they are to be made; suitable thicknesses can be ascertained by simple testing. The thickness can be, for example, in the range 0.003-0.012 inch and especially 0.0060.012 inch.

Our invention also consists in a process for the manufacture of the valved bags of the invention from a continuous length of lay-flat tubing of thermoplastic material, that comprises bringing to a work station a bag length from the end of the continuous length; cutting an aperture in the wall of the bag near to one end of the bag length; securing a patch-piece to the said bag wall to cover the aperture, internally or externally, to provide a filling sleeve between the patch-piece and the bag wall; and sealing the walls of the bag together at or towards at least one end of the bag length across the width of the bag, the bag length being detached from the length of the lay-fiat tubing at some stage during or after the manufacture.

The end or ends of the bag unit may be sealed before or after the patch-piece has been secured into position, but at least the end that is close to the aperture is preferably left open until the patch-piece is in place, so that it may be more easily positioned and secured.

Since valved bags in the form in which they are used normally have had their mouths closed, leaving the valve as the only place of entry into the bag, it is preferred to seal the open bag mouths as a part of the manufacture.

In a particular process according to the invention, the end portion of a continuous length of the lay-flat tubing is brought to a Work station and sealed across its Width to define an open-mouth bag, a wall of the bag is cut so as to provide an aperture through which the bag can subsequently be filled, and a patch-piece is secured to the said bag wall to cover the aperture and to provide a filling sleeve between the patch-piece and the bag wall, the bag being detached from the length of lay-flat tubing and the open end preferably being sealed at some stage after or during the manufacture.

The process of this invention is particularly suited for continuous operation as is shown in the example which appears later in this specification. Where the process is operated in a continuous manner it is very convenient to obtain the patch-pieces required by cutting off successive portions from a strip of thermoplastic material fed to the work station.

The sealing of adjacent portions in the processes of this invention can be achieved in any suitable manner that will bond together the portions to be joined in such a way that the contents for which the bag is designed cannot escape between the said portions. The sealing can be achieved, for instance, by sewing, by high frequency electric welding, by hot melt adhesives or by the application of heat, with applied pressure if necessary, to the said portions. The use of heat is commonly referred to as heat-sealing. Where the portions to be heat-sealed are of polythene it is convenient to use heat and applied pressure in conjunction and this process is particularly suitable for the sealing of polythene bags. Where polyvinyl chloride is used as the thermoplastic material, adjacent portions can conveniently be sealed together by means of high frequency electric welding.

Where sealing is achieved using heat, accidental sealing of adjacent portions not intended to be sealed can be avoided by inserting a suitable former between those adjacent portions before the heat-sealing is carried out. The surfaces, at least, of the former should be of a material that will not stick to the thermoplastic material or have a deleterious eflect upon it under the conditions used for the sealing. A suitable former for use in the heat-sealing of polythene is a thin support, for instance of glass fibre, coated with polytetrafiuoroethylene (PTFE) or with a silicone rubber.

In the processes described in the following example, which illustrates our invention, the lay-flat tubing was simultaneously cut and heat sealed. However, the cutting and heat sealing can, if desired be accomplished in separate steps. The sealing can conveniently be done using reciprocating hot sealing bars.

Example The example describes one cycle of a continuous process for the manufacture of valved bags of polythene as shown in FIGURE 4 of the accompanying drawings (to which reference will be made) from a length of lay-flat polythene tubing having a thickness of 0.010 inch and a tube width of 22 inches.

One end of the lay-fiat tubing was fed horizontally to a work station and heat-sealed across its width about 24 inches from the end, thereby defining an open-mouthed bag attached at its closed end to the remainder of the tubing. There was then inserted into the mouth of the bag a former consisting of a sheet of glass cloth impregnated with PTFE. The following slits were then cut in the uppermost wall of the bag: the aperture in the bag wall was formed as a straight slit (one edge of which is shown at 32) about 6 inches long, transverse to the edge of the bag mouth and extending from a point about 1 inch from and at an angle of about 80 to that edge; and a number of subsidiary slits, parallel to each other and to the edge of the bag mouth, were cut in the same uppermost bag wall, each extending from the aperture and each about 3" long. These subsidiary slits defined series of parallel fingers, 38, in the bag wall. There was no waste produced in making the slits; they were made by means of a cutter which was brought down on to the uppermost wall of the bag, the blades of the cutter co-operating with corresponding depressions in the former to facilitate the cutting.

A patch-piece, 33, was then secured to the uppermost bag wall as follows. A continuous strip of polythene film (having a thickness of 0.010 inch and a width a little greater than the length of the principal slit) was fed to the work station and a rhomboidal piece (8 inches long at seam edge 36) was cut off to provide a patch-piece. This patch-piece was placed lengthways on the bag wall in the position shown, and was then heat-sealed to the bag wall at 34, 35 and 36, leaving the fourth edge unsealed. The sealing thus defined a filling sleeve between the patch-piece and the outer surface of the bag wall, the filling sleeve together with the principal slit providing a duct extending from the exterior of the bag, at a position near to one side of the bag wall, to the interior of the bag.

After removing the former from the bag, the bag mouth was closed by heat-sealing the two opposed bag walls together along their coincident top edges at 39; the closed bag was then severed from the end of the length of lay-flat tubing, leaving the latter with an open end ready for feeding on to the former in the next cycle of the process.

When the finihed bag was filled with granular artificial fertilizer and inverted, substantially none of the granular contents escaped from the filling sleeve.

Sacks constructed in accordance with this invention are particularly useful for transporting and storing powdered or granular materials, especially when good protection from moisture and contamination is required, and particularly where outdoor storage of the filled sacks is necessary. They are, for example, especially useful for the packing of fertilizers, chemicals, polymer granules and powders, and animal feeding stuffs.

I claim:

1. A bag made of plastic sheet material, said bag comprising: opposed side walls heat-seamed along all initially open side edges, one of said side walls being provided with a filling aperture near but spaced from one end of the bag; a patch-piece, of the same material and substantially the same thickness as the said side walls, covering said aperture and heat-seamed along an edge portion to the inside surface of said side wall and free of said side wall along another edge portion remote from said aperture thereby forming a filling sleeve which is open at one end to the interior of the bag and which is open at the other end to the outside of the bag through said aperture, said heat seams between said patch-piece and side wall, being distinct from the heat seams between the opposed side walls, whereby heat seams involving three layers and consequent weakness of the seam areas are avoided; and an extension piece, of thinner material than the said side Walls, heat-seamed to said other edge of said patch-piece so as to cover said one open end of said sleeve, whereby escape of the contents of the bag when full is prevented.

2. In a bag made of plastic sheet material and having opposed side walls closed by seaming along all initially open sides, one of said side walls being provided with a filling valve at one end thereof, the valve being formed by an aperture in the wall of the bag and a patch-piece secured only along a portion of its edges: to the wall of the bag to cover the aperture and to form a filling sleeve between the bag wall and the patch-piece, said filling valve having one open end defined by said side wall and the unsecured edge portion of said patch-piece and an opposite open end defined by said aperture, the improvement consisting in that the patch-piece is secured to the inside surface of the bag wall by seams that are each distinct from the seams between the opposed walls of the bag, and in that an extension piece of thinner material than the patch-piece is secured to the end of the patch-piece near said one open end of said sleeve, said extension piece extending over said one open end.

3. A valved bag as claimed in claim 2 in which the patch-piece is of the same material and of the same thickness as the bag wall.

4. A valved bag as claimed in claim 2 in which said one open end of said sleeve is substantially at right angles to the top of the bag.

5. A valved bag as claimed in claim 2 formed of 0003-0012 inch thick polythene film.

6. A valved bag as claimed in claim .2 in which the open ends of the valve are transverse to the adjacent edge of the bag.

7. A valved bag as claimed in claim 6 in which the filling sleeve lies across the width of the bag and close to the top edge of the bag wall.

References Cited by the Examiner UNITED STATES PATENTS 810,349 l/O6 Rogers -9 2,643,049 6/53 Bartelt 229-62 2,682,902 7/54 Metzger.

2,799,314 7/57 Dreyer et al. 150-0.5 2,870,954 1/ 59 Kulesza 22962.5 2,880,925 4/59 Klasing et al. 229---53- 2,927,722 3/60 Metzger 229-62.5 3,051,209 8/62 Gonzalez l50-9 3,052,588 9/62 Anderson et al 156-252 3,053,723 9/62 Plack 156252 FOREIGN PATENTS 819,498 10/51 Germany.

OTHER REFERENCES German Application, 1,014,830, printed 8/29/57 (KL 54b).

GEORGE O. RALSTON, Primary Examiner.

WALTER A. SCHEEL, FRANKLIN T. GARRETT,

Examiners. 

1. A BAG MADE OF PLASTIC SHEET MATERIAL, SAID BAG COMPRISING: OPPOSED SIDE WALLS HEAT-SEAMED ALONG ALL INITIALLY OPEN SIDE EDGES, ONE OF SAID SIDE WALLS BEING PROVIDED WITH A FILLING APERTURE NEAR BUT SPACED FROM ONE END OF THE BAG; A PATCH-PIECE, OF THE SAME MATERIAL AND SUBSTANTIALLY THE SAME THICKNESS AS TH SAID SIDE WALLS, COVERING SAID APERTURE AND HEAT-SEAMED ALONG AN EDGE PORTION TO THE INSIDE SURFACE OF SAID SIDE WALL AND FREE OF SAID SIDE WALL ALONG ANOTHER EDGE PORTION REMOTE FROM SAID APERTURE THEREBY FORMING A FILLING SLEEVE WHICH IS OPEN AT THE END TO THE INTERIOR OF THE BAG AND WHICH IS OPEN AT THE OTHER END TO THE OUTSIDE OF THE BAG THROUGH SAID APERTURE, SAID HEAT SEAMS BETWEEN SAID PATCH-PIECE AND SIDE WALL, BEING DISTINCT FROM THE HEAT SEAMS BETWEEN THE OPPOSED SIDE WALLS, WHEREBY HEAT SEAMS INVOLVING THREE LAYERS AND CONSEQUENT WEAKNESS OF THE SEAM AREAS ARE AVOIDED; AND AN EXTENSION PIECE, OF THINNER MATERIAL THAN THE SAID SIDE WALLS HEAT-SEAMED TO SAID OTHER EDGE OF SAID PITCH-PIECE SO AS TO COVER SAID ONE OPEN END OF SAID SLEEVE, WHEREBY ESCAPE OF THE CONTENTS OF THE BAG WHEN FULL IS PREVENTED. 